public class Pair<K, V> {
    private K first;
    private V second;

    public Pair(K first, V second) {
        this.first = first;
        this.second = second;
    }

    public K getFirst() {
        return first;
    }

    public V getSecond() {
        return second;
    }

    public void setFirst(K first) {
        this.first = first;
    }

    public void setSecond(V second) {
        this.second = second;
    }

    public void swap() {
        Object temp = first;
        first = (K) second;
        second = (V) temp;
    }

    @Override
    public String toString() {
        return "(" + first + ", " + second + ")";
    }

    public static void main(String[] args) {
        Pair<String, Integer> pair = new Pair<>("Hello", 42);
        System.out.println("Before swap: " + pair);
        pair.swap();
        System.out.println("After swap: " + pair);
    }
}